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"""Reference implementation for reflection in gRPC Python."""

import threading

import grpc
from google.protobuf import descriptor_pb2
from google.protobuf import descriptor_pool

from grpc.reflection.v1alpha import reflection_pb2

_POOL = descriptor_pool.Default()

def _not_found_error():
  return reflection_pb2.ServerReflectionResponse(
      error_response=reflection_pb2.ErrorResponse(
          error_code=grpc.StatusCode.NOT_FOUND.value[0],
          error_message=grpc.StatusCode.NOT_FOUND.value[1].encode(),
      )
  )

def _file_descriptor_response(descriptor):
  proto = descriptor_pb2.FileDescriptorProto()
  descriptor.CopyToProto(proto)
  serialized_proto = proto.SerializeToString()
  return reflection_pb2.ServerReflectionResponse(
      file_descriptor_response=reflection_pb2.FileDescriptorResponse(
        file_descriptor_proto=(serialized_proto,)
      ),
  )


class ReflectionServicer(reflection_pb2.ServerReflectionServicer):
  """Servicer handling RPCs for service statuses."""

  def __init__(self, service_names, pool=None):
    """Constructor.

    Args:
      service_names: Iterable of fully-qualified service names available.
    """
    self._service_names = list(service_names)
    self._pool = _POOL if pool is None else pool

  def _file_by_filename(self, filename):
    try:
      descriptor = self._pool.FindFileByName(filename)
    except KeyError:
      return _not_found_error()
    else:
      return _file_descriptor_response(descriptor)

  def _file_containing_symbol(self, fully_qualified_name):
    try:
      descriptor = self._pool.FindFileContainingSymbol(fully_qualified_name)
    except KeyError:
      return _not_found_error()
    else:
      return _file_descriptor_response(descriptor)

  def _file_containing_extension(containing_type, extension_number):
    # TODO(atash) Python protobuf currently doesn't support querying extensions.
    # https://github.com/google/protobuf/issues/2248
    return reflection_pb2.ServerReflectionResponse(
        error_response=reflection_pb2.ErrorResponse(
            error_code=grpc.StatusCode.UNIMPLEMENTED.value[0],
            error_message=grpc.StatusCode.UNIMPLMENTED.value[1].encode(),
        )
    )

  def _extension_numbers_of_type(fully_qualified_name):
    # TODO(atash) We're allowed to leave this unsupported according to the
    # protocol, but we should still eventually implement it. Hits the same issue
    # as `_file_containing_extension`, however.
    # https://github.com/google/protobuf/issues/2248
    return reflection_pb2.ServerReflectionResponse(
        error_response=reflection_pb2.ErrorResponse(
            error_code=grpc.StatusCode.UNIMPLEMENTED.value[0],
            error_message=grpc.StatusCode.UNIMPLMENTED.value[1].encode(),
        )
    )

  def _list_services(self):
    return reflection_pb2.ServerReflectionResponse(
        list_services_response=reflection_pb2.ListServiceResponse(
            service=[
                reflection_pb2.ServiceResponse(name=service_name)
                for service_name in self._service_names
            ]
        )
    )

  def ServerReflectionInfo(self, request_iterator, context):
    for request in request_iterator:
      if request.HasField('file_by_filename'):
        yield self._file_by_filename(request.file_by_filename)
      elif request.HasField('file_containing_symbol'):
        yield self._file_containing_symbol(request.file_containing_symbol)
      elif request.HasField('file_containing_extension'):
        yield self._file_containing_extension(
            request.file_containing_extension.containing_type,
            request.file_containing_extension.extension_number)
      elif request.HasField('all_extension_numbers_of_type'):
        yield _all_extension_numbers_of_type(
            request.all_extension_numbers_of_type)
      elif request.HasField('list_services'):
        yield self._list_services()
      else:
        yield reflection_pb2.ServerReflectionResponse(
            error_response=reflection_pb2.ErrorResponse(
                error_code=grpc.StatusCode.INVALID_ARGUMENT.value[0],
                error_message=grpc.StatusCode.INVALID_ARGUMENT.value[1].encode(),
            )
        )

